Hi Paula,
Thanks for writing to T2T. You don't mention what grade you're teaching,
but the following suggestion would hopefully work for you. Using the "take
away" interpretation of subtraction, you can observe that (using your
example), we want to "take away" 3/5, but don't have any "fifths" to take
away. If we took 1 of the "wholes", and cut it into fifths, we would then
have 1 whole and five fifths. Now take away 3 of the fifths, and what we'd
have left is 1 whole, and two fifths,
So, 2 - 3/5 = 1 5/5
and 1 5/5 - 3/5 = 1 2/5
Hope this helps,
-Ralph, for the T2T service